Carburizing box and like article



Bet-rented Nov. 7, W333 'Ellwlll Harry 1L. lFrevert and Francis E. Foley Padelphia, Pa. I

No Drawing. Application January 2, 1932 Serial No. 58%,565

5 (Claims. (Cl. 263%9) The object of the invention is to provide articles such as carburizing boxes and annealing boxes of such composition that they will meet the exacting requirements for such boxes. There 5 are other articles of manufacture which in use are subjected to conditions similar to those to which carburizing and annealing boxes are subjected and which may be, therefore, grouped in the same class, such other articles including salt to bath pots, lead bath pots, soot blowers, grate bars and tube supports.

The following are examples of compositions which have been found to accomplish the objects sought:

0 .70 .48 .58 .55 .3 .45 .40 .28 5.55 2.44 8.5 8.6 5.5 8. 0. 8.58 1. 2.01 .96 .87 1.25 :.85 1.5 1.24 Or 22.19 24. 85 23. 23.5 30. 25. 25. 24.24 Cu 5.55 6.88 5.5 10.85 8. 8. s. 0.74 Al 1.58 2.5 2.12 2.07 2. 2. 2. 1.80

The composition set forth in the last of the above vertical columns is preferred in most cases. a The following three vertical columns disclose, 5 respectively, the approximate permissive maximum ranges of proportion of the several constituents, the ranges of proportions that will cover most efiicient compositions, and the pre ferred ranges of proportions:

silicon and aluminum may be used. It is advis-.

able, however, not to use maximum proportions of silicon and aluminum, where it is important, as it often is, to avoid any substantial degree of brittleness.

The alloy steel described is an alpha steel having an exceedingly high critical temperature (in the neighborhood of 1800 F.) and in which the hysteresis gap between critical temperatures of heating and cooling is practically suppressed. In the class of articles hereinbefore specified,

if the temperature to which the articles in use are subjected should habitually exceed the critical point of the ferrous alloy specified, the articles will not crack, as such articles usually do under such conditions, for thereason that because of so the high critical temperature of cooling the change of size occurs at a high temperature at which the alloy is plastic.

The use in small proportions of metals, other than those specified, which are commonly alloyed with iron, is not excluded; but the addition of none of them is required in orderto secure the advantages hereinbefore detailed.

As, in the case of all or mostof the articles specified, the trade demands that they shall be to reasonably priced, another of the advantages of the invention is that the articles contain a high proportion, and ordinarily a dominant proportion, ranging from over half to two-thirds or more, of iron, and that none of the other constituents in in used in sufficient proportion to render the product uncommercially expensive. The most expensive constituent, because of its relatively large proportion, is chromium; but even the content of chromium may be reduced to between one-fifth and one-fourth of the entire composition without sacrifice of utility for most uses, this relatively small percentage of chromium be- .ing in fact preferable in cases where toughness jected to a temperature above such high critical temperature.

What we claim and desire to protect by Letters Patent is: 1. A carburizing box composed of a ferrous alloy embodying the following constituents in the proportions specified: carbon .05-1.2%, manga- -nese 210%, silicon .25-5%, chromium 20-45%,

copper over 5-15%, aluminum 1-5%, the balance being substantially iron. 2. A carburizing box composed of a ferrous alloy embodying the following constituents in the proportions specified: carbon .15-.8%, manganese 29%, silicon .752.25%, chromium 21-30%,

iron and chromium together; the percentage of chromium being over one-third and less than one-half the percentage of iron. 5. A carburizing box composed of a ferrous alloy embodying the following constituents in the proportions specified: carbon .05-1.2%, manganese 29%, silicon .43%, copper over 5-12%, aluminum 1-3%, the balance being substantially iron and chromium; the percentage of chromium being over three-tenths and less than six-tenths the percentage of iron.

HARRY L. FREVE'RT.

FRANCIS B. FOLEY. 

